This invention relates to mixtures of fluorinated hydrocarbons and more particularly to constant boiling fluorocarbon mixtures which comprise 1,1,2-trichlorotrifluoroethane and cis-1,1,2,2-tetrafluorocyclobutane. Such mixtures are especially useful as compression refrigerants, particularly in systems using centrifugal or rotary compressors.
The refrigerant capacity per volume pumped of a refrigerant is largely a function of boiling point, the lower boiling refrigerants generally offering the greater capacity at a given evaporator temperature. This factor to a great extent influences the design of refrigeration equipment and affects capacity, power requirements, size and cost of the unit. Another important factor related to boiling point of the refrigerant is minimum cooling temperature desired during the refrigeration cycle, the lower boiling refrigerants being used to achieve the lower refrigeration temperatures. For these reasons, a large number of refrigerants of different boiling temperature and capacity are required to permit flexibility of design and the art is continually faced with the problem of providing new refrigerants as the need arises for new capacities and types of installations.
The lower aliphatic hydrocarbons when substituted by fluorine and chlorine are well-known to have potential as refrigerants. Many of these fluoro-chloro hydrocarbons exhibit certain desired properties including lower toxicity and nonflammability which have resulted in extensive use of such compounds in a large number of refrigeration applications. 1,1,2-trichlorotrifluoroethane and trichloromonofluoromethane are two available chlorine-fluorine hydrocarbons known to be useful in water chilling applications with centrifugal compressors. There is a recognized need for refrigerants with boiling point temperatures between the relatively high boiling point temperature of 1,1,2-trichlorotrifluoroethane, plus 47.6.degree. C. at atmospheric pressure, and the boiling point temperature of trichloromonofluoromethane, plus 23.78.degree. C. at atmospheric pressure, in order to have available refrigerants of good performance in varying capacities.
It would be possible to achieve the desired boiling point by mixing two refrigerants with boiling points above and below the desired one. In this case, for example, mixtures of trichloromonofluoromethane and 1,1,2-trichlorotrifluoroethane could be used. It is well known, however, that simple mixtures create problems in design and operation because of segregation of the components in the liquid and vapor phases. This problem is particularly troublesome in systems using centrifugal compression because of the large quantities of liquid usually found in the evaporator.
To avoid such segregation problems, the art is continually searching for new azeotropic or constant boiling blends such as the constant boiling fluorocarbon blends disclosed in U.S. Pat. Nos. 3,607,755; 3,470,101; 3,640,869; 3,505,232; 3,634,255 and Canadian Pat. No. 832,341.
An object of the present invention is to provide new mixtures with boiling points between that of 1,1,2-trichlrotrifluoroethane and trichloromonofluoromethane suitable for use as refrigerants.
More particularly, it is an object of the present invention to provide refrigerant systems with a capacity between the refrigeration capacity of 1,1,2-trichlorotrifluoroethane and trichloromonofluoromethane and which are useful as compression refrigerants, particularly in systems using a centrifugal or rotary compressor.
Another object is to provide new, low boiling azeotropic or constant boiling mixtures which are useful in producing refrigeration in those systems in which cooling is achieved by evaporation in the vicinity of the body to be cooled and in which because of the nature of the system, the problem of segregation is critical.